1. Field of the Invention
The present invention relates to a compound eye photographing apparatus for photographing a subject at a plurality of photographing positions and a control method therefor. The invention also relates to a program for causing a computer to perform the control method for the compound eye photographing apparatus.
2. Description of the Related Art
A method for generating a distance image that represents a stereoscopic shape of a subject is proposed. In the method, the subject is photographed by a compound eye camera having a plurality of cameras, then corresponding points, which are pixels corresponding to each other, between a plurality of images (a base image obtained by a base camera and a reference image obtained by a reference camera) obtained by the photographing are searched for (stereo matching), and the distance from the base camera or reference camera to the point on the subject corresponding to the pixel is measured by applying the principle of triangulation to the positional difference (parallax) between the pixel in the base image and the pixel in the reference image corresponding to each other, thereby generating a distance image.
In the mean time, for a compound eye camera, various types of controls, such as focus control, exposure control, photographing control are performed, as well as the distance measurement described above, based on the result of determination if a target subject is included in a plurality of images obtained by the compound eye camera. In order to perform such controls for a compound eye camera, various methods for determining if a target subject, such as a face or the like, is included in a plurality of images obtained by the compound eye camera are proposed. For example, U.S. Pat. No. 6,999,896 (Patent Document 1) describes one of such methods. In the method, a plurality of sensors, namely a compound camera and a millimeter wave radar, is provided, then based on normal error distributions with respect the position and velocity when the same target object is detected by each of the sensors, first and second probabilities that each of the detected objects is the same target object in terms of the position and velocity are calculate from the errors in the identified positions and velocities, and a third probability is calculated based on the first and second probabilities to determine that each of the detected objects is the same target object when the third probability exceeds a predetermined threshold value.
Further, Japanese Unexamined Patent Publication No. 2007-110498 (Patent Document 2) proposes a control method of a compound eye camera in which detection of a specific subject, such as a face or the like, and various controls, including focus control, exposure control, and the like, are performed based on an image obtained by one of a plurality of cameras thereof.
The method described in Patent Document 1, however, requires a sensor other than a compound eye camera which complicates the device configuration. Further, it is necessary to calculate the probabilities which requires a longed time. In the method described in Patent Document 2, various controls are performed based on an image obtained by one camera, thus the controls are performed even when a subject commonly presents in the photographing ranges of all of the cameras is not included in the image. Here, it is often the case that a subject presents in the photographing range of one camera but not in the photographing range of another camera is not so important for the photographer. Consequently, in the method described in Patent Document 2, various controls may sometimes be performed based on a minor subject included only in the image obtained by one camera.
The present invention has been developed in view of the circumstances described above, and it is an object of the present invention to enable simple determination as to whether or not a predetermined common subject, such as a face or the like, is included in a plurality of images obtained by a compound eye photographing apparatus.